Diesel engines may generally be classified as slow-speed, medium-speed or high-speed engines, with the slow-speed variety being used for the largest, deep draft marine vessels and in industrial applications. Slow-speed diesel engines are typically direct coupled, direct reversing, two-stroke cycle engines operating in the range of about 57 to 250 rpm and usually run on residual fuels. These engines are of crosshead construction with a diaphragm and stuffing boxes separating the power cylinders from the crankcase to prevent combustion products from entering the crankcase and mixing with the crankcase oil. Medium-speed engines typically operate in the range of 250 to about 1100 rpm and may operate on the four-stroke or two-stroke cycle. These engines are trunk piston design, and many operate on residual fuel as well. They may also operate on distillate fuel containing little or no residua. On deep-sea vessels these engines may be used for propulsion, ancillary applications or both. Slow speed and medium speed marine diesel engines are also extensively used in power plant operations. The present invention is applicable to them as well.
Each type of diesel engine employs lubricating oils to minimize component wear, remove heat, neutralize and disperse combustion products, prevent rust and corrosion and prevent sludge formation or deposits. Experience has shown, however, that no single lubricant formulation can provide optimum protection against all of the various deleterious conditions to which an engine may be exposed. Therefore, lubricants typically are formulated to provide at least satisfactory performance for the range of expected engine operating conditions. For some lubricant applications such as in lubricating cylinders in crosshead diesel engines that employ all-loss lubrication systems and combust heavy fuel oil with widely varying sulfur contents, the engine lubrication requirements vary to such a large degree and with sufficient frequency that one lubricant formulation may not provide adequate performance over the full range of operating conditions. This inability can result in at least increased engine maintenance needs and more typically unnecessary expense as a result of repair costs, down time and excessive oil usage. Thus there is a need for being able to vary the composition of a lubricant in response to an engine's actual lubrication requirements.
One object of the invention is to provide lubricant components for real time varying all-loss, diesel engine's cylinder lubricant properties in accordance with the engines operating requirements.
Another object of the invention is to provide a low speed diesel engine oil with improved acid-corrosion protection for operation during conditions when corrosive wear is high.
These and other objects will become apparent from the detailed description which follows: